Skin pricking lancets are well known in the art. Many such lancets comprise a needle having a sharp tip at one end and being embedded in a body at the opposite end, with the tip of the needle protruding from the body. Such lancets are used to obtain a small blood sample for analysis. Many lancet firing devices have been devised to make the procedure of skin pricking as simple and safe as possible. Such firing devices typically include a holder for holding the lancet body, and a firing mechanism. The firing mechanism is configured to push the needle of the lancet into the skin for a predetermined distance or using a predetermined force. An example of such a firing device is described in EP1204371.
The lancets themselves tend to be cheap, disposable items. Generally, they should not be reused. However, firing devices of the type described above tend to be reusable, and so the lancet holder is configured to allow an old lancet to be replaced by a new lancet. Firing devices of one manufacturer should, as far as possible, be useable with lancets produced by another manufacturer.
Lancet bodies are typically cylindrical in shape. The lancet holders commonly have a corresponding cylindrical socket into which the rear end of the lancet body can be pushed to secure the lancet within the holder. However, variations in the diameter of lancets between those supplied by one manufacturer and those supplied by another manufacturer, and even variations in the diameter of lancets from the same manufacturer can lead to problems in securing the lancet. For example, sometimes the lancets are secured too loosely, and other times the lancets are too large to fit into the cylindrical socket.
EP0925021 attempts to address this problem by providing a cylindrical socket with a split down the wall of the cylinder and a coil spring disposed around the wall to constrict the socket. If a lancet body has an external diameter slightly larger than the internal diameter of the socket, then the socket walls expand slightly to accommodate the larger lancet body, and are then constricted by the spring about the lancet body to hold it in place. However, this solution is not ideal if the lancet body is slightly too small. Furthermore, this solution is not ideal if the lancet body is not cylindrical but is another shape such as frustoconical.